Berliner Beiträge zur Archäometrie Seite 33-68 2008
A case study on the granite monuments decay under seawater. The reco vered relics in Alexandria - Egypt.
T AREK NAZEL AND JOSEF R IEDERER Rathgen research laboratory, Berlin, Germany.
Abstract:
The deterioration of granite monuments under seawater has been studied on fo urteen granite arti facts from more than thirty - six relics from variable materia ls were reco vered from the sea, some of them was ex hibited and some was stored in the open Roman theater, in the national museum of Alexandria, in the marine museum and in the Egyptian museum. The study concerns with the determination of some petrophy sical, mineralogical. chemical and petrographic characteristics of both weath ered samples from the studied recovered artifacts and fresh from Aswan quarries from where the stone of these artifacts was extracted to allow having a sight into the hi sto ry of the g ranite stone o f arti facts before cxtracting and being as a monument and also before exposing to the new circumstances under seawater.
XRD, XRF and pola ri zed mi croscope were used for the determinati on ofthe last three mentioned characteri stics of samples respectively.
All these analyses and investigati ons aim to find which deterioration causes and pro cesses acted in the granite artifacts under seawater in relation to study of the marine environment in Alexandria and the human impact on it as a comparison with the quar ries g ranite.
Two main kinds of deterioration morphology were found affecting the recovered arti facts, thc First conccrns with thc aesthetic va lues of the monuments and this includes the attachment of cerals with the artifacts surfaces (fig.l) and the metal corrosion stains whi ch were produced from the contact with metals or organic materials under seawater for a long time (fig.2), the secend kind of deteri oration morphology refl ects the sevcre state o f cleterioration which the artifacts sutfer from. Four granite decay fo rms were found in our case beleng to th is kind of morphology, these are:
I) The superficial detachments and this includes three different names according to the detached layers d imensions: plaques, plaquettes and scales (figures: 3, 4 and 5 respecti ve ly), these different last mentioncd names can be explained according to (8. Silva, et al. , 1996) as follows: plaques occupy a big arca and they are more than 5 mm thick, plaquettes are thinner and scales are thinner and smaller in area, and the last is the commonest decay form in altnost recovered artifacts.
2) Sand disaggregation (fig.6).
33 3) Etch-pitting or (alveolization) (fig.7).
4) Fissuring (fig.8).
Figure 1: thc enormous amount of Figure 2: the mctal corrosion stains attached Corals on granite artifact disperse on a part of granite artifact surface. surface.
Figure 3: the biggcst dimension of superficial dctachmcnt (plaques). dent view.
Figure 5: the smallest form of su perficial detachment (thc scale for mation).
Figure 6: sand disaggregation form.
34 Figure 7: a scvere dcgree of the Figure 8: the fissuring form. etch-pitting form (alveolization)
As a result from a statistical study of the decay forms only few cascs were found having the last three mentioned forms of decay as a comparison with the first one. The first kind of deterioration morphology is not serious and unless required for aes thetic purposes or to revcal inscriptions there should bc no necd to remove it.
As regard to the significance ofthe second kind of morphology as a comparison with the first, the present work studies it and searchcs the causes and processes which Iead to its different forms.
Many factors and mechanisms cooperated in sequence long processes to producc the last mentioned granitc decay forms. The first step in these processcs begins in the quarries before the birth of artifact.
The abovc mentioned analyses demonstrated that the all studied artifacts suffered from severe physical and chemical alteration in their rock-forming minerals and these were the main serious factors which lcd to the last mentioned decay forms of granite and thc first kind of alteration was the most serious.
Twcnty four new formation minerals were detected with XRD analyses as alteration products in the studied samples from the artifacts versus five minerals in the studied samples from thc quarrics.
I ntroduction:
By the mid fifth century A.D. as the Grcck geographer Stt·abo (Strabo, XVII.) men tioned, the most of ancicnt Alexandria was destroycd by a series of earthquakcs and swallowed by the sea.
Betwcen 1994-1 998, thc Franco-Egyptian group discovered two main sites of sub merged artifacts beneath the watcr ofthe East harbor of Alexandria and not more than 350m distance between them: the first is the site ofthe submerged ruins ofthe famous ancient lighthouse of Alexandria- the Pharos-one ofthe seven wonders ofthe ancient world, more than 2500 artifact were discovercd in an area of more than 25 km' and
35 wait for rai si ng, the second site is the site of the remain s of the submerged Potlemic roya l quarters including the remnants of thc famous fabled palace of Cleopatra, more than 3000 artifacts are believed that scattered along the sea bed from variable shapes and materials.
The marine environment of Alexandria was studied, specially the area of thc two archaeological sites.
Many environmental problems have grown rapidly in Alexandria in recent decades. thc cnormous growing in population and population density, the urban enlargement and the industrial development are the main reasons ofthese problems, the city affects dramatically its marine environment by discarding all its Iiquid wastes, domestic and industrial into the sea, and by the physical alteration of the coast line by coastal engi nccring works. The total cumulative volume of waste water disposcd of into the sea from al l point sources along this stretch of coast is about equal to the Nile outflow from the Rosetta outlet: roughly 9 million mlfday, that is, 3,33 km 1/yr. but th is is not river water. A daily volume of more than one million cubic meters of mixcd scwage watcr is drained from thc city. About one third of this is disposed of without any tre atment into the Eastern and Western harbor and their surroundings.
Thc Qait Bey outfall (fig.9), located a few hundred meters from the discovcred site of thc lighthouse, releases 200,000 m' ofwaste water pcr day. The East harbor is the reci pient of 7 outfalls. This semi-closed harbor rcmains pcrmanently turbid, and water vi ibility is drastically reduced (Y. Halim and F. Abou Shouk, 2000).
Mediterrane an Sea
0 5km '""=-=-' Figure 9: The main outfalls: I) Qait Bey and Eastern harbor outfalls: about 200 x IO }.m}.d-' untreated waste water. 2) Lake mariout main basin outfalls about 500 x I O'.ml.d·' primary treated: + 300 x IO'.m' .d·' untreated municipal waste water. 3) Mex pump station on Umoum drain about 7000 x I O'.m}.d ' agricultural drainage water mixed with the overflow from L. Mariout main basin. 4) EI Tabya pump station to Abu Qir Bay: about 2000 x I O'.m'.d·' industrial Waste water. (A fter Y. Hai im and F. Abou Shouk, 2000)
36 Objcctives:
Although there are a Iot of archaeological marine sites were discovered in ditferent countries in the world the seawater effect on stone is stilllittle known and there is no attempt was achieved to introduce widely an explanation ofthe decay process ofstone under seawater. Therefore the ultimate scope ofthe work was to understand the decay processes which affect the gran ite monuments under the seawater and also after reco vering in order to be in the posi ti on to propose thc appropriate conscrvati on practices specially for granite and generally for the other stones.
Materialsand Mcthods:
Sampies from two variable varieti es from Aswan granite quan·ies from where the stone of the studied artifacts was extracted were col lected, the first variety is rose coarse granite and thc second is red coarse granite, and they were dcnoted by ASGQ and AOGQ symbols rcspectively.
These quarries sampl es were prepared to study in relation to depth, where one core sample of 20 cm long from every variety was cut (accord ing to technique proposed by .1. Delgado et al. , 1996) longitudinally in two hal ves and aft er split in cross thin slabs at I cm interva l. Also samples from fourtecn recovcred granite artifacts were coll ected. Taken into consideration that these artifacts were chosen with sufficient precision to represent the all kinds of thc decay morphologics and also the all varie ties of granite. The choose of these artifacts depended on a precise visual observation of more than twenty-seven gran ite recovered objects. The chosen artifacts were divi ded according to the decay morphologies whi ch affected by to two groups:
I) the first group: includes eleven artifacts affected by The superficial detachments ( cight of them have scale form, two have plaqucttes and one has pl aques), taken into account that this group contains nine arti fac ts belong to Aswan rosc granite variety where this variety is the commonest in the all recovcred artifacts and only two arti facts belong to Aswan red granite variety. Thcy were denoted by symbols SGM (1- 9) and OGM 10 and 11 respectively.
11) the second group: and thi s inc ludes three arti facts, every one of them affected by one of the following decay morphologics: Sand disaggregation, Etch-pitting or (alveolization) and Fissuring, and the three artifacts belong to the rose variety and werc denoted by symbols SGM 12, 13 and 14 respective ly.
The sampling varied in the two groups according to the decay morphology as shown in table 1.
Thc petrophysical properlies of stone are one of the most important factors which aceeierate or delay its decay.
37 Table I Dcscription of the studied samplcs C ROUPI CROUPII Sampie symbol Descri1>tion Sam1>lc symbol Description A the gran itc monumcnt Substrate A thc granitc monument substrate ß the weathered detachcd layer w Wcathercd surfacc c dcposits were found at the granitc substrate detached layer interfa'c (personal observation)
Also from which we ca n determine to a !arge extent the degree of alterati on and to what extent the consolidation process will bc succced.
For these purposes some of pctrophysical properlies of samples from the studied arti facts and quarries were determined such as real and bulk densi ties. opcn porosity, saturation coefficient and water sorption.
X-ray di ffraction (XRD) technique was carried out on powdered specimens using equipment Philips PW 1729 to detennine thc mineralogical compositi on of both of the fresh and the weathered samples.
In order to determine thc change of quantity and thc behavior of the major, minor and trace elements during the deterioration proccsses X-ray fluorescence (X RF) techni que was performed using equi pment Oxford ED 2000 energy di spersivc with Oxford Expert Ease software. To determi ne the petrographic characteri sti cs and the features of weathering and altcrati on a Iot ofthin secti ons of fresh and weathered samples were studied and photographed under the polari zin g microscope using (Zciss Licht mikroskop).
Causes and mechanisms of decay process:
Thc decay process of artifact depends on two main vari able reacti ve things: the mate ri al of artifact and thc environment whi ch surrounds by it.
Therefore the sites ofthe studied artifacts within the marine environmcnt associated with the rcaction interfaces at which the artifacts affected either directly or indirectly were classified in an imaginative figure (fig.IO), these reaction interfaces in our case study were classified as: atmospheric air I seawater surface, seawater I artifacts, arti facts I sea water I seabed sediments, artifacts I sediments I interstitial water and artifacts I scawater I sediments I interstitial water interfaces, in re lation to the reaction between Alexandria city and its marine environment. lt is very important at the beginning to describe chemi cally thc normal and thc abnormal marine environment using Eh-pH as shown in (fig.ll) in order to propose the relationship between Eh and pH in the studied environment.
And also it is very im portant to expect the position of zero Eh in rcspcct to the sea water I sea bed sediments as shown in (fig.ll) where we suggest - as a results from
38 seawatersurface/ atmospheric air interface
Sea water
Artifacts/seawater interface at depths 6-8-10 m
Artifacts/Seawater/ Sea bed sea bed sediments interface
artifactlseawater/ Artifacts/sediments/ sediments/ interstitial water interstitial water interface at depths 10, 5-11 m Sedimentsand its interstitial sea water
Figure 10: A classification ofthe sites ofthe studied arti facts associated with the che mical rcactions interfaccs
L og concont:r-at:ion ('t.Ot:RI s.alinfty) Ao•t.rict:vd rncu• fne anoxic onvf,.onmon"t
Figure 11: Chemical characteristics of some marine environments. (From C.Pearson, 1987) the study of Alexandria city and its effect on thc marine environment and also from artifacts samples analyses -that the zero Eh position is at the sea bed sediment surfa cc as shown in (fig. 12. section b).
Whilst for ease of understanding, the decay of granitc monuments wh ich recovered from the seawatcr has been divided into two mainly stages as follows:
The first dccay stage is pre excavation and this includes before and during sin king. Tbc second decay stage is after recovering.
39 We introduce the first stage only in this paper, and the second will be introduced scparately in another pape r.
A scientific view ofthe first stage will be sug gested in this paper applied on our case study, Ia) where we suggest that the decay process may Water surface bc takc place at this stage in three main se quence steps as foll ows:
The first step: (Physical alteration)
(b) The stone artifact may be carrying thc first Water surface cause of decay before or during its birth and certainly before sinking under water.
When a rock is extractcd from a quarry to be used in a monument, this breaks up with an evo lution process that began some mill ion years (c) ago at the time o f thc rock Formation and has Figure 12: Diagram showing rela been carried out in a condition close to equili ti ons of zero Eh surfacc (redox brium. Change in natural conditions very often Ievel) to depositional interface. produce a marked disturbance in this evolution Wherc secti on (b) represents the and aceeierate rock decay (J. Delgado, 1978). suggested position ofzero Eh in our case study. (From C. Pearson, 1987) ln other words, many of rocks were exposed to stresses in the earth crust during the geologic agcs (E.M. Winkler, 1973), and also rocks can be exposed to stresses during quarry or artifact sculpture operations.
When the artifacts in a contact with water such as in our case, a reaction takes place at the artifacts I scawater interfacc where these Stresses pl ay thc most serious role in thc fi rst proposed step of grani te decay as foll ows:
The tectosil icate group which incl udes the most important primary minerals of gra nite, quartz and fcldspar, is basically made up of Sio: - tctrahcdral units linked at their corners by Si-0-Si bonds. The Si-0 bond may be under stress, and if it can be broken, a micro-crack in the Silicate may extend. Three sequence reactions between water and a Si-0-Si bond under stress at a crack tip can be shown in (fig.l3).
The three sequence reactions can be explained as follows: a) A water mo lectlle in the vicinity of thc stress point will be attracted to the Si-0 bond, so that its oxygen (0.) bonds to the sil icon via the oxygen lone pairs. One of its hydrogen can hydrogen bond to the bridging oxygen (0.).
40 :------~-- ·- /------; - -. -;---- ~-sl.,/ 1 b) This reaction involves si- " 1/ 11 multaneous proton and elec- ' 1 SI I I : _ s·, b ? : tron transfer, so that new 11 0 1 "- ______1 " /' 11 bonds are formed, one bet- 11 0 1 1 11 1 "' ween (0.. ) and silicon, and /s'""" y ), 1 one betwecn hydrogen and I /I'--... I : (Ob).The original bridging / " ...... -s,·,, ~~ ...... - " bond between (Ob) and sil i- ~ _____ .!.a.!. ______<~~- ______< ~'- __: con is destroycd. c) Thc final rcaction is the Figure 13: The proposed mechanism ofstress-corro breakage of the hydrogen sion cracking. (A fter W. Bland and D. Rolls, 1998) bond betwecn (0.) and the transferred hydrogen to give a Si-0-H group on each fracture surface. The combination of a weakened bond and constant stress Ieads to micro-crack extension. (W. Bland and D. Roll s, 1998, Based on T.A. Michalske and S. W. Freiman .. 1983).
When the arti fact has already affccted by micro-cracks before sinking, thesc micro cracks will be developed according the Griffiith theory of crack development, where he proposed that the fracture of th e brittle material begins when the tensile stress at the tip ofan (elliptical) crack provides sufficient cnergy to overcome the encrgy ofthe crack surface (W. Bland and D. Roll s, I 998).
There is no doubt that, the micro-cracking proccss plays an important role in the for mation of the last mcntioned granite deterioration morphologies specially in the case of fissuring and also in the supcrficial detachment formation morphology, where the depth, the length and the shape of the micro-crack controls at least the thi ekness and thc arca of the dctached layers to producc thc different three forms of thc Superfici al detachment. To evaluatc their serious influence on the granite it wi ll be enough to say that about 2% of voids under thc form of fi s ures rcducc the granite strength in about 50% (J. Delgado, 1978).
The micro-cracks enablc also seawater to penetrate into the arti fa ct to play serious decay processes which will be explained in the second step.
The second step: (Chemical alteration)
The alteration process is the main process at the external layers of ani Facts where Ieads to the different form o f the superficial detachment morphology of grani te, and wi thout its role, these forms may be not takc place, and also this proccss affects the internal layers and thc substrates of artifacts but in a lower degree.
The authors suggest that two important processes Iead to the alteration of granite under seawater, the first one is chemical process, and this is the main process of alteration, thc second is biochemical process, and this is considered an accelerator of alteration.
4 1 I) The chemical process:
The most serious agent of the chemical process is the seawater itself. Seawater is the complex solution which includes the universal solvent (water) whi ch has the most important property (the unique molecular dipolar), enormaus particulate solid matters, salt ions, and dissolved gases. The main chemical reaction begins at the artifacts I sea water interface as follows:
The seawater attacks the granite drastically, wherc penetrates through pores, cleava ges and micro-cracks. Then water can attack the granite in three simultaneaus pro cesses according to (F. C. Loughnan, 1969) as follows:
I) The breakdown of the parent mineral structures with the concomitant release of cations and silica. The released silica may be in more or less polymerized forms. 2) The removal in solution of some of the (released) constituents. 3) The reconstitution of the residue with components from the environment such as water, oxygen and carbon dioxide, to form new minerals which are in stable or metastable equilibrium with the present environment.
- Mechanism of breakdown of parent mineral structures:
l"t•hlspolt" 'l: urrflco.' H I 0-1·1 , remova l of potassium permits >O I H Si-OH aluminum, which originally is II I 0 ( 0 - H present in tetrahedral coordi 11 I + H AI-OH + KOH nation with oxygen, to assu )0 I Ii 0 -H me its preferred octahedral Ii I 0( H coordination and, as a result H I 0-H
42 polyhedra may form amorphaus colloids but with aging they become oriented into the structures of the secondary minerals such as clays and oxides.
The ionic mobility was summarized by Loughnan( I 969) as in table 2.
In gcneral, the final balance involves a reduction in calcium, sodium and potassium and a corresponding increase in water, aluminum and iron. At the end of the process, the mass lass may be 60% or cven greater if the water is free to percolate and to carry ofT in solution the elements released by chemical action of environment agents (R. Pellizzer and G. :,abatini, 1976).
But in our case we propose that other secondary chemical reactions may bc prevent the state of equilibrium and proceeds the main chemical reaction beyond it. Thc first secondary reaction takes placc at the atmospheric air I seawater interface where the hydrogen ion can be rcnewed by the reacti on between atmospheric carbon dioxide and seawater as follows: co2 is dissolved in scawater (COz H COz (solution)), and reacts with water to form carbonic acid (C02 (solution) + H20 < > H 2C0.1).
And although thc pH of the scawater is buffered by the action of the HCOj·ICO/ equilibrium, this buffering systcm is weakcr or vi rtually absent depending on local circumstances (C. Pearson, I 987), ln our case this local ci rcumstances are the cease less discarding ofwaste, industrial, and domestic liquids from Alexandria city into the seawatcr as widely mentioncd in the introduction and this reaction affects indirectly the artifacts which were scattercd on the sca bed.
The sccond secondary chemical reaction takes place at the artifacts I seawater I seab ed sediments interface as follows: The clay minerals is one of the inorganic compo nent of the seabed scdiments (C. Pearson, 1987), and because of unsaturated valen cies of atoms and ions at their surfaces, isomorphaus Substitution within thcir lattices, or exposed hydroxyl groups, the clay minera ls possess negative charges. They endea vor to attain neutrality by adsorption of cations. which although bonded to the surfa ces of the minerals, may be readily exchanged for other cations in So lution. the mea-
Table 2: Rclati\c mobitity ofthc common cations Cations Rate of leaching I Ca , Mg -. Na Read il y lostunder lcaching condition 2 K Rcadily lostunder lcaching condition but rate may bc retarded through fixation in thc illitc structurc 3 Fe Rate of loss eiependent on the redox potential and dcgree of leaching 4 Si' Slowly lost under lcaching conditions
5 Ti' My show limitcd mobility ifreleascd fromthe parcnt minera t as Ti(OH)4; if in the TiO! form , immobile 6 Fe' Immobile undcr oxidizing conditions 7 Al' Immobile in the pH range of 4.5-9.5
43 sure of the ability of clays to adsorb cations is termed the cation exchange capacity ( cec) (F.C. Loughnan, I 969). Tn the absence of bases they will be surrounded by H' causing the pH to fall (J.M. Cronyn, I 990), and according to Ioughnan, I 969 where the adsorbed ion is hydrogen, the clay behaves as weak acids or (colloidal acids) which attack the silicate minerals, and this reaction affect also indirectly the artifacts which are on the sea bed or under it but in different degrees.
JI) The biochemical process:
The biochemical process takes place at two reaction interfaces, the first at artifacts I seawater I sea bed sediments and this concern with the artifacts which scattered on the sea bed, the second at the artifacts I sediments I interstitial water and this concern with the artifacts which wcre buried under sediments at depth between 50 to 100 cm.
Marine aerobic bacteria, fungi, algae and Iichens represent the biodeterioration fac tors at the first reaction interfacc where the Im·gest accumulation of these organisms specially bactcria are at the seawater I sea bed sediments interface, andin our case the artifacts were found near the sea surface at depths 6, 8 and I 0 m where the environ mental parameters (oxygen, light, salinity, temperature, depth, pressure, currents and nutrients) are suitable for living thesc organisms.
Sound stonc is not readily invaded by bacteria, and fungi also start their activity during the beginning of weathering but bacteria can break up silicate minerals as quickly as fungi do (E. M. Winkler, 1973). As soon as artifacts enter the seawater they are covered with a film of diatoms or bacteria and the cycle of biodeterioration starts (C. Pearson, I 987). May be the most serious species of bacteria which affcctcd the studied granite artifacts are: the bacteria which can mobilize si lica and silicate and the Iron bacteria specially ferrooxidans where play as an oxidizer of iron from ferrous ions to ferric ions (E. M. Winkler, 1973), (G. Caneva, M. N ugari and 0. Salvadori, 1991 ).
Fungi can attack silicate minerals especially the micas, Orthoclase and others by the production of carbonic, nitric, sulphuric and some weaker acids (E. M. Winkler, 1973), (K. Sterflinger et al. , 1996).
Lichens exerted considerable biological alteration on mineral suhstrates and it appe ars that contact between Iichens and Substrate are mainly due to the fungal symbiote, specially Silicolous Ii chens which prefer silicate rocks (L. Galsomies et al. , 1996), (E. M. Winkler, I 973).
The depletion of potassium from intcrlayer positions in the biotite material may be due to the chemical attack of Ii chens acids and other acid substances occurring in the Iichen thallus, thus the low pH and chelating properlies of the Iichens substrates Iead to the protonization and abundance leaching of K (C. Aseaso and J. Wierzchos, 1996). Algae also appear capable to the dislocation and precipitation of metals at rock sur faces (W. Bland and D. Rolls, I 998).
44 An other biochemical process takes placc at the artifacts I sediments I interstitial water where the anaerobic bactcria are dominant and as mentioncd in the introducti on, and illustrated in (fig.9) many outfall s add their Ioad of suspended matter and a variety of contaminants to the marine environment in Alexandria, such materials, on sinking to the bottom, contribute to blankering whatcvcr artifacts are lying on the seabed. They also cause hypoxic conditions at the bottom in some places, enhancing the processcs asso ciated with the absence of oxygen. including anaerobic bacteri al processes (Y. Hat im and F. Abou Shouk, 2000).
The sulphate reducing bacteria, cspccially Desulfovibrio desulfuricans (G.caneva, M. Nugari and 0. Salvadoti, 1991) inhabit fine-grained anacrobic mud where oxygen is absent, and they employ dissolved sulphate present in interstitial water as a terminal elec tron acceptor in the oxidation of organic matter, producing H2S as a metabolic product (G. Amoroso and V Fassina, 1983). According to the distribution of sulphate reducing bacteria in thc marine sediment which can bc shown in table 3, we can say that about 330 to 400 bactetia per gram sediment accumulate at the depths of the buried artifacts.
Sulphate reduction can be described as follows:
In pH 7-8, H,S ionizes: H,O + H,S < • H30 ' + HS· forming a weak acid which may lower the pH (C. Pear on, 1987).
Thc Eh and pH cantrot the mineral association in sediments and subsequently also intluence artifact material. The reducti on of Fe· 3 to Fe·' for example greatly increases their solubility. There are four ways in which the solubility of various ions prc Tablc 4: The bchaviour of ion specics as function scnt in seawatcr is altered when subjected of Eh and pH. Dcpcndent on Eh Dcpendent on pH to Eh or pH changes within a natural Ion Na' 0 0 range, these arc shown in table 4 as Eh K ' 0 0 Ca•• 0 0 Tahlc 3: Typical distribution of sulphate reducing Mg' 0 0 bactcria in mari ne sedimcnt. Cl" 0 0 Dcpth into Bactcria pcr sca bed (cm) gram scdirnent Br·· 0 0 0- 2.5 38 000 000 .. 0 0 2.5 - 5.0 940 000 CO; 0 X 10- 12.5 88 000 PO,· 0 X 23 - 25.5 36 000 OH 0 X 35- 37.5 2 400 Fe' X 0 48- 51 -100 Fe' X 0 74- 76 180 Mn' X 0 99- 102 330 Mn' X 0 150- 203 250 s· X X 201 - 203 130 SO/ X X 251 - 254 290 X indicatcs dependcnce. and 0 indicatcs Iack of (After: C. Pcarson. 1987) depcndencc. (After: C. Pearson. 1987)
45 and pH dependent, Eh and pH independent showing no influence, Eh dependent only, and pH dependent only (C. Pearson, 1987)
The role of concretions (corals) in the biochemical process is considered an assistant role, and according to (Pearson, 1987) sulphate reducing bacteria occur in the con cretion, and also when the artifacts become covered by thick layers of concretions,
this will restriet the oxygen supply and allow the accumulation of H2S under them.
We can propose that there is a biochemical process may be take place at both ofthe arti facts I seawater interface and the artifacts I sediments I intcrstitial watcr intcrfacc, this process is the biochemical chelation or exchange uptake of ions, where the marine envi ronments always contain algae, fungi and Iichens as factors oftbis reaction at the first interface and some organic materials, representing both of plant rootlets or their secre tion and the population of decaying plant debris as factors of the reaction at the second.
And it is probably that components of this organic materials are capable of comple xing metallic ions in much the same manner as EDTA (ethylenediaminetetraacetic acid) the best known chclating agent in analytical chemistry (F. C. Loughnan, 1969) where the very small H cation produced by the rhizomes of Iichens and roots of higher plants easily exchange with most meta! cations in solution and the transfcr can occur though a network of colloidal particles by a contact -exchange mechanism (E. M. Winkler, 1973), (G. Caneva, M. Nugari and 0. Salvadori, 1991). An imaginative figu re can be shown as a representation of the chelation process under seawater, see (fig. 15).
Plants can absorb meta! cations for their nutrition and in micro-organisms, mineral ions can be accumulated in the cells, for example the Iransformation of mica to ver miculite is performcd by fungi with a process ofthis kind (K ions are exchanged with Na ) (G. Caneva, M. Nugari and 0. Salvadori, 1991 ).
The third step: (Decay morphologies evolution)
After the physical and the chemical alteration of granite minerals which were explai ned at tl1e first and second steps, and as a result of them the granite became contai ning a Iot of fissures and also a Iot of clay minerals, therefore we propose that the
Seabed Plants roots Organic materials and Granite decaying roots debris object U nder sea bed sediments and interstitial water
Figure 15: An imaginative view of the che1ation process under seawater.
46 dccay process in this step affects severely the new Formation minerals, and also we propose that all or most oF granite decay morphologies arise in thi s proposed step which involves two processes, as follows:
I) physiochemical process:
This process may be one oF the most important causes of thc granite superFicial detachment Formation, where concerns with the intlucnce of water on the clay mine rals, amJ their behaviour under this influence ca bc cxplained as follows:
Clay crystals are vcry small in size (below 2 micron) and each crystal is composed of a series oF waFers (several hundred of them). In the most common clays (e. g. Montmorillonite or illite) the waFer is composed oftwo layers oF sili ca and one layer of alumina interposed betwccn them. Thc wafers carry hydroxyl ( -OH) g ro ups and negative charges, due to the presence of impurities (e. g. iron) which are able to takc the placc of silicon and aluminium cven iF they have less positive charges. As a con sequence, positive ions, like sodium in Montmorillonite, are frequently trapped bet ween wafers and water is ablc to penetratc the crystal as it is attracted by the hydro xyl groups as shown in (fig.l6).
The access of water results in the incrcase o f the distance between wafers and so in the swelling ofclay (fig.l7) (G. Torraca, 1982).
The clay minerals difFer in their reaction with water, where thcre are expanding clay minerals and nonexpanding, and that is attributed to their chemical composi tion for example according to Torraca, 1982 illite contains calciurn betwecn wafers and this ensures a stronger attraction betwccn them. The swclling of illitc is, the reFore, smaller, and also kaolinite is very pure clay which contains no iron and has a two layers wafcr (one ofsilica and one ofalumina). As a consequence the wafers have no negative charge and there are no ions trapped betwccn them. The wafers are kept together by relative -o-w ly strong hydrogen bonds and water may be unable to 1- Fe -Fe - Fe! separate them. -o-w Although the expanding pro Figure I 6: diagrammatic representation of a clay perty of some kinds of clay wafer ( From G. Torraca, 1982) minerals plays an important role in thc superficial detach ment Formation of granite. there is also another property plays an effective rolc in thi s decay morphology, this pro Normal state of clay Swelling of clay Contraction perty is the plasticity, where Figure 17: diagrammatic reprcscntation of the swel according to G. Torraca, 1982 ling of clay (from G. Torraca, 1982) the all clays are plasti c when
47 wet because the thin crystals .- ·- ·-·-·-·-·-·- ·- ·- ·-·-·-·-·-·-·- ·-·-·- ·-·. slide easily over one another > > under a slight pressure as in (fig.l8). Figure 18: diagrammatic representation of the slide Therefore, we propose that of clay wafers (from G. Torraca, 1982). granite superficial layers de tachments always take place at the clay accumulation places in the g ranite structure or in another word, at the most altered grains.
lt is important to say that (the personal observation) may be support our proposal where obvious amounts of very soft clay deposits were found in the all detached lay ers I granite Substrates interfaces of the studied artifacts. and the results of the last mentioned performed analyses ensured that as will be cxplained in the discussion.
U) Mechanical process:
This process is suggcsted as the most serious process which Iead to sand disaggregation, alveolization and fissuring morphologiesandalso to flaking offthe superficial detached layers. This process involves two factors, the first is physical, and the second is biophy sical, it seems that the second is most effective and its mechanical action is faster.
- The physical factor:
The physical factor of the mechanical process is the action of seawater and sediments movement. According to Pearson, 1987 the deposits in shallow coastal waterare sands (with particle size 62 11 -2000 11), silts (4 11 -62 ~t) and clays (less than 4 11). No doubt that, sands have the most effect because of their bigger size and higher hardness.
The mechanical action of water and sediments may be not serious in the case of intact granite artifacts, but in our case, andin this stage of deterioration the granite artifacts suf fer ti·om severe alteration and a !arge amount oftheir essentialmineralswas converted to soft clay minerals. This then according to WinkJer, 1970 very susceptible to attack with water and sediments and it is rare !hat clay minerals survive intact on a shipwreck.
- The biophysical factor:
This factor includes Marine fungi, algae, Iichens and borers, these organisms and animals play an important role in the mechanical detachment of superficial layers, in the extending of cracks and fissures and in thc evolution of sand disaggregation and Etch-pitting (alveolization) morphologies.
Fungi can penetrate the granite and their cells can be found even in a depth of several mm under the surface where they are using the weakest point in granite for their attack:
48 the micas can easi ly be removed mechanically leaving caves (K. Sterflinger et al., 1996), these caves contribute in the forming ofalveolization. Lichens hyphae do not only pene trate microfractures and intergranular surfaces along the easicst paths, but also able to cross any minerat including quartz in any direction (M. Delmonten et al., 1996).
Lichens can pcnetrate to depth 2 mm and to 3-4 cm into cracks (L. Galsomies et al., 1996). Green algae has also the ability to fracture the granite rocks, these microcracks defined flakes between 2 and 4 mm thick (\V. Bland and D. Rolls, 1998).
The marine burer:" ur the boring animals are one of the most dangeraus biodcteriora tion factors, wh ich include borers of soft rocks such as the clay minerals (the weat hering products of granite) and another of ha rd rocks such as the granitc (the essen tial material of the studied arti facts ).
These marine animals may burrow under the scales causing the layers to fl ake off (C. Pearson, 1987). Wikler, 1973 reported a description of the mechanical boring mcchanism from Ansell , 1969 as follows: The strong foot of the animal can anchor the end ofits foot near the cxit ofthe hole against the wall by expanding its foot wh ile the sharp-edgcd shell abradcs the stone by turning back and forth araund its long axis.
The angcl wings (Pholas) and false angel wings (Petricola) can cause damagc in the clay minerals by their mcchanical drilling action through rotation of the sharp edged shell (C. Pearson, 1987).
Winkler ( 1973) reported that, the angel wings dig at a rate of 12 mm. a ycar, with a total depth of about 150 mm, and he also reported thc observation of warme ( 1969) about the Pholads, where hc observed that a higher population density of Pholads in soft rock than in hard material.
Sea Urchins (both of genus Ech inus and Euc idaris) attack any stone, hard or soft (C. Pearson, 1987).
The mechanical of their damagc was described by Winklcr, ( 1973) as follows: Echinus and Eucidaris are able to dig in by means of abrasion, sinking their sharp teeth , located in the center at the bottom of their body, into the rock underneath. The boring rates for Echinids wcre observed to bc as much as I cm/year in Iimestone and faster in weathercd granite (E. M. Winkler, 1970). (C. Pearson, 1987).
Results:
The petrophysical properties of the studied monumental and quarries samplcs can be secn in table 5.
The XRD analysis results of the studied fresh core samples from Aswan rose granite quarries and Aswan red granitc quarries and of the studied weathered samples from the recovered artifacts can be seen in tables 6, 7 and 8 respectively.
49 Also a comparison between the XRD patterns ofthe all examined slabs from the rose and the red core samples with the relation to the profile depth and also an example for the studied artifacts XRD patterns can be seen in figs. 19, 20 and 21 respectively. The full results which were obtained from the chemical analyses with XRF for both of the two core samples rose and red and fo r the studied samples from artifacts can be seen in tables 9, 10 and ll respectively.
In order to study the behaviour of the major, minor and trace elements and to deter mine the variation of their concentrations and also of L.O.l. with depth figs. from 24 to 31 for the two core samples, figs. from 32 to 39 for the samples from artifacts group Tand figs. from 40 to 47 for the samples from artifacts group II can be shown. The results of the petrologic study can be seen in table 13 and also some petrogra phic weathering features can be seen in figs. from 48 to 55.
Table 5: T hc pctroph sical charactcristics of thc studied samples
ASGQ ADGQ SGM I SG~ I 2 SGM3 SG~ I 4 SGMS SGM6 SG:V17 SGM~ SGM9 DG~IIO DGMI I SG M12 SG~I13 SGMI4 ßD 2622 265 1 2637 2558 2596 2531 2489 2549 2553 25 32 251 6 2545 2465 2597 2581 254 1 lW 2596 2629 2585 2478 2509 2461 242 6 2505 2489 254 3 2438 2548 2544 2484 2454 2403 or 0.81 0.99 1.97 3.12 3.35 2,77 2.54 1,72 2.48 3.4 3. 1 3,86 3.06 3,7 4.9 5,41 SC 54 52 87 72 57 74 62 62 I 66 83 62 9t 83 89 93 91 ws• 0.24 0.2 0.66 0.91 0.77 0.83 0.65 o.43 I o.66 1. 1 0,8 1.39 1.04 1.55 1.85 2.05
0 0 BU: ßulk dcnsity ( Kg,ml): RD: Real dcnsity (Kg m'): 01,: Open 1mrosity ( 0): SC: Sat uration coeiTiCtl..'nt ( u): according 10 RIL E1\.1 191-:0. * WS: \.Vater sorplion (%); according to ASTM C·97··0 , 1958. legend: ASC.Q: Aswan rose grnnile quarri cs. ADGQ: Aswan red gra·1itc quarrics. SGM: rosc g.ranitc monumcnt, UG~1: red granitc monumcnt.
Tablc 6: Mineralogical c haractcristics of Aswan rose granite quarries in relation lO the profile depth. SAMPLE ESSENTIAL M INERALS ACCESSORY MINERALS SECONDARY MINERA LS ASGQI Quartz. K fel dspar, Plagioclasc, Muscovite. Hornblende, Rutile, Epidote. Vcrmiculite, Dickitc. Biotite. Sphene, Zircon, Magnetite. Nacritc. Apatite. Titanite. Allanitc. ASGQ2 Quartz, K fcldspar. Plagioclasc. Muscovitc, [Jornblcndc. Rutile. Epidote, Vermiculite. Dickitc. ß iotite. Sphene, Zircon, Magnetite. Nacritc. Apatite. Titanite. Allanite. ASGQ3 Quartz. K fcldspar, Plagioclasc, Muscovitc. llornblende, Rutile, Epidotc. Venniculite. Dickite, Biotite. Sphene. Zircon, Magnetite. Nacrite. Apatite, Titanite, Allanite. ASGQ4 Quartz. K fe ldspar. Plagioclase, Muscovite. Hornblende. Rmile. Epidote. Vermiculite, Dickite. ßiotitc. Sphene, Z ircon. Magnetite. Nacritc. Apatite, Titanite. Allanite. ASGQ5 Quartz. K feldspar. Plagioclase. Muscovite. Hornblende. Rutile. Epidote. Vcrmiculite. Dickite. Biotite. Sphene. Zircon. Magnetite. Nacrite. Apatite. Titanite. Allanite. ASGQ6 Quartz, K fcldspar, l'lagioclasc. Muscovite, llornblendc. Rutile. Epidotc, Vermiculite. Dickitc. Biotite. Sphene. Zircon. Magnetite, Nacrite. Apatite. Titanite. Allanite. ASGQ7 Quartz. K feldspar. Plagioclase. Muscovite, Hornblende, Rutile, Epidote. Vermiculite. Dickitc. ßio litc. Sphene, Zircon. Magnetite, Nacritc. Apatite. Titanite, Allanite. ASGQ8 Quartz, K feldspar. Plagioclase, Muscovite, Hornblende, Rmile. Epidote, Vermiculite. Dickite. Biotite. Sphene. Zircon. Magnetite, Apatite. Titanite. Allanitc.
50 Tablc 6: Mineralogical characteristics of Aswan rosc granite quarrics in relation to the profilc depth. SAM PLE ESSENTIAL MINERALS ACCESSORY MINERALS SECONDARY MINERALS ASGQ9 Quartz, K fcl ASGQ13 Quartz, K fcld,par. Plagioclase. Musco' ite, llornblendc, Rutile. Epidote, Vermiculitc, Dickit~. Biotitc. Sphene. Zircon. ~lagnctite, Apatite. Tit.nitc. Allanitc. ASGQI4 Quartz. K feldspar. Plagioclasc, Muscovitc. llornblcnde, Rutile. Epidote, Vcrmiculite, Dtc~ite. ßiotite. Sphene, Zircon. Magnetite. Apatite. Tit Table 7: ~lincralogical characteri;lics of Aswan red granite quarrics in relation to the profile dcplh. SAMPLE ESSENTIAL t'.II NERALS ACCESSORY MINERALS SECONOARY MINERALS ADGQI Quartz. K feld>par. Plagioclase. ßiotitc. Mu;covite. Hornblende, Epidotc, Venniculite, Nacrite. Rutile. Sphene. Zireon. Goethite. Magnetite. Apatite. Titanite. Allanitc. ADGQ2 Quartz, K feldspar, Plagioclasc. Biotite. Musco\ itc. Hornblende, Epidote, Vcrmiculite, Nacrite, Rutile. Sphene. Zircon, Goethite. Magnetite. Apatite. Titanite. Allanitc. ADGQ3 Quartz. K feldspar. Plagioclase. ßiotite. l'vlusco,·ite. Hornblende. Epidote. Vermiculite. Nacrite. Rutile, Sphene. Zircon, Goethite. Magnetite. Apatite. Titanite. Allanitc. ADGQ-l Quartz. K feldspar. Plagioclasc. Biotite. MuscO\ ite. Hornblende. Epidotc. Venniculitc. Nacrite. Rutile, Sphene. Zircon, Goethite. Magnetite, 1\patite, Titanite, Allanitc. 51 Table 7 : Mineralogical charactcristics of Aswan red granitc quan·ies in relation to th e profile depth. SAMPLE ESSENT IAL MINERALS ACCESSORY MINERALS SECONDARY MINERALS ADGQ5 Quanz. K feldspar, Plagioclase. Biotite, Muscovite, Hornblende, Epidote, Vermiculite. Naerite, Rutile, Sphene, Zircon. Goethite. Magnetite. Apatite. Titanite. Allanite. ADGQ6 Quartz. K fcldspar, Plagioclasc. ßiotite. Muscovite. Hornblende, Epidote, Vermiculite. Nacrite. Rutile. Sphene. Zircon, Goethite. Magnetite. Apatite, Titanite. A llanitc. :t\1JGQ7 Vuartz,I 52 Table 7: Mineralogical charactcristics of Aswan red granitc quarrics in relation to thc profile dcpth. SAMPLE ESSENTIAL MINERALS ACCESSORY MINERALS SECONDARY MINERALS ADGQ19 Quartz, K feldspar. Plagioclase. ßiotitc. Muscovite. l lornblendc. Epidotc. Vcrmiculitc. Goethite. Rutile, Sphene. Zircon, Magnetit~ . Apatite, Titanite. Allanitc. ADGQ20 Quartz, K fcl Table 8: Mincralogical characteristics ofthe srudied rccovercd artifacts in relation to thc profilc depth. MORI'liO- SIIMPLE ESSENTIAL MINERALS !ICCESSORY MINERALS SFCONDARY M INI: RALS LOGY OF DETERIO- RATION Scale SGMIA Quartz. K fcl 53 Table 8: Mincralogical characteristics ofthe swdied recovered artifacts in rclation to thc profile depth. MORPIIO- Si\MPLE ESSENTIAL MINERALS ACCESSORY MINERALS SECO DARY MINERALS LOGY OF DETER IO- RATION SGMJB Quartz, K feldspar. Muscovit~:, Zin.:on, Epidotc. Vcrmiculite. Plagioclasc. Biotitc. lvlagnctitc. Titanite. Allanitc. Dickite. Nacri te, Halloysitc, Chlodte-vcrmiculitc Montmorillonitc. lllitc, Scpiolitc. Zoisite. Prehnite. Calcite. Kaol inite. Goethite. SGM3C Quartz. K fcldöpar. Muscovitc. Zircon. Epidote. Vermicul itc. Plagioclasc. ßiotite. Magnetile. Tilanite, Allanite. Dickitc, Prchnitc, lllite, Scpiolitc. Scalc SGM4A QLtartz, K leldspar. Muscovitc. 1-! ornblcndc. Epidotc. Vcrmiculitc. Plagioclase, Biotite. Rutile. Sphene. Zircon. Dickitc. Chlorite-vcnniculite- Magnetite. Apatite. Tit::mite. Montmorillonüe, Zoisite, Allanitc. Prchnite. Cordicrite. Calcite. SGM4B QuartL. K fcldspar, Muscovitc. llornblcndc. Epidotc. Vcnniculitc. Plagioclase, Biotitc. Rutile, Zircon. Magnetite. Dickite. Nacrite. 1-! alloysitc, Apatite, Ti tanite. Allanite. chlorite-vcrmiculite- Montmorillonitc. Glauconitc, lllitc, Scpiolitc. Zoisitc, Prchnitc. Kaolinite. Goethite. Hcctoritc. Cordicritc. Calcite. SGM4C Quartz. K fcldspar. Muscovite. llornbkndc. Epidote. Vcrmicu l it~. Plagioclasc. Biotitc. Rutile. Zircon, Magnetite, Dickite. Nacritc, chloritc· Apatite. Titanite. Allanitc. vcrmicul itc- Montmori ll o- nitc, Glauconitc. lllitc, Scpiolite, Zoisit e. Prehnitc, Kaolinite. Cordieritc. Calcite. Scalc SGMSA Quart7. K fcldspar, Muscm ite, Rutile. Sphene, Epidotc. Vermiculite. Plagioclasc. Biotitc. Ztrcon, Magncrite, Apatite. Dickitc, Nacrite, chlorih:- Tttanitc. Allanite. ven11iculitc- Montmori llo· nitc, Glauconite. lllitc. Sepiolite. Zoisitc. Prchnitc. Calcite. SGM5ß Quartl. K fcldspar. Muscovitc, Rutile. Zircon, Epidote, Vermiculitc. Plagioclasc. Biotitc. Apatite, Titanite, Allanitc. Dickitc, Nacritc, chlorit c- vcrmiculitc- Montmorillo· nitc. Glauconitc. lll itc, Scpiolite. Zoisitc. Prchnitc. Calcit e. SGM5C Quartz, K fcldspar. l'vluscovite. Rutile. Sphene. Epidotc, Vc rmiculitc. Plagioclase, ßiotitc. Zircon. Magncti rc , Apat ite, Dicki tc, Nacritc, chl oritc· Tiranitc. Allanitc. Ycnniculitc- ~1oll1m orillo- nitc. Glauconitc. lllite. Scpiolitc. Zoisitc. Prehnite Calcitü, Kaolinite, Cordicritc. Plaqttettcs SGM6A Quart z, K fcldspar. Muscovite. llornhlcndc. Epidoh.:. Vcrmit::ulitc. Plagioclasc, Biotite. Rutile, Zircon, Magnetite, Dickitc, Nacritc. chlori1c- Apatite. Titanite. A llanitc. vcrmiculitc- Montmorillo- nitc. Glattconitc. lllite, Sepiolitc. Zoisitc, Cl inozoisitc, Prchnite, Kaolinite, Goethite. Calcite. 54 Tablc 8: Mineralogical characteristics ofthe sntdicd recO\cred artifacts in relation to the profilc d epth . MORPHO- SAMPLE ESSENTIAL MINFRALS ACCESSORY MI'IERALS SECONI)ARY MI NFRALS LOGY OF DETER!O- RATION SGM6B Quaru. K fe!dspar. Musc01 itc. llornblcndc. l:jn~otc. Vcrmiculitc. Plagiocla;e. Bi o111c. Rutile. Zorcon. i\lagnctitc. Dickitc. Nacrite. chloruc- A;mtitc, Titanite, Allanitc. 'crmiculitc- Montrnorillo- nitc, Glauconitc. ll lit e, S~p i olitc. Loisitc. Clinozob 11 t'. Prehmtc. Kaolinite. Goethite. Calcite. Halloysite. Monttl'>orillonitc. Hectoritc. Sericitc. ~p onitc . Cordicritc. \ SGM6C Quan1, K feldspar. Muscovitc. llornhlcndc, Lpidotc. Vcrmiculitc. '\ Plag•oclasc, ßiotnc. Rutile. Zircon. ~ 1a g netitc , Dickite, N:1crite. chloritc- ApaliiC, Titanite, Allanite . \CrmicuiJte- l\1ontmonllo- \ nite. Glauconitc. lllite. Scpiolitc. 7.oisitc. \ Cl inozoi,itc. Prehnitc. Kaolinite. Goethite. Cakite, \ Halloysitc. Montmorillonitc. llcctoritl!, Sericitc. Saponitc, l'al)gor;knc. Cordicntc. Scalc SGM7A Quartz. K fe!dspar. ~tu scov n c, llornblcndc, Epidotc. Vcrmiculnc. l'lagioclasc. Uiotitc. Rutile, Sphene, Zircon. Dickite, 1-htlloysile, chlorite- Magnetite. Apatite. Titanite, 'crmicul itc- Montmorillo- Allanne. nilc. lllnc. Sepiolitc. Zoisitc. l'rchnitc. Cordierite. Calcite. SGM7B Quartz. K fel d>par. Ivluscovitc. llornblcndc. Epidote, Vcrmiclllite, Plagioclasc. Biome. Rutile. Sphene, Zircon. Dickite. Nacritc. H allo~; it e. Magnetllc. Apat1 tc . Titanite. chlorilC-\ crmiculite- Allanite. Mommorillonitc, lllite. Scpiolitc. Zoisile. Prchnite. Cordierite. Calcite. Gibbsite. Kaolinite. SGM7C Quart/ , K fcl PhtcjUCS SGM8A Quant, K fcldspar, MuscO\ nc. I !ornblcndc. Epid01e. Vcrmiculitc. Plagioc!ase. Bi01itc. Rutile. Sphene, Zircon. Dickitc. acritc. l lalloysitc, ~ l ag n ct ll e. Apatite T11anitc. chloritc-' crmiculitc- Allanllc. Montmonllomte. !IIIIe. Zobitc, Clinozoisitc. Prehnilc. SGM813 Quartt. K feld,p•lr. 1\.luscm He. Hornblende. Epidotc. Vermiculitc. Pla giocla~e. ßiotltc. Rutile. Sphene. Zircon. Dickitc, Nacritc. llalloysnc. Magnetite. Apatite. Titanite, ('hloritC- VCI'ITIICUIIIL:· Allanitc. Montmorillonitc. lllitc, Zoisire. Clinozoisitc. Prchnitc. Scpiolitc. Montmonllonitc. Glauconitc. Gibbsite, Nontronitc. 55 Table 8: Mincralogical charactcristics ofthe studied recovcrcd artifacts in relation to the profile depth. MORI'IIO- SAMPLE ESSENTIAL MI ER ALS ACCESSORY MINERALS SECONDARY :v!INERALS LOGY OF DETERIO- RATION SGM8C Qumtz. K feldspar. 1\luscovitc, llornblende. Epidotc. Vermiculite. Plagioda,e. ßiotitc. Rutile. Sphene. Zircon. Dickitc. Nacritc. llalloy,ite. Magnetite. Apatite. Titanite. Chlorite-' crrn1cuhte- Allanitc. Montmorillonitc, lllitc. Zoi>itc. Clinoz01s1tc. Prchnitc, Scplolitc, Montmorillonite, Glauconitc. Gibbsite. NontrOilltc. Kaolinite. Goethite. llectoritc. Saponitc. Bcidellite. Plaquencs SGM9A QuartL, K fcldspar, Museovite. llornblcndc. Epidotc, Vcrmiculitc, Plagioclasc. ßiotitc. Ruule. Sphene. Zircon. Diekite. Nacritc. llalloysitc. ~lag nctitc. Apatite. Titanite. Chlorite. lllitc. Zoisuc. Allanitc. Clinozoi>~ te. Prchnite. Sepiolitc. Glauconite. Kaolinite. G~thite. Calcite. SGM9B Quarll. K fddspar. Mu,covitc. llornblcnde. Epido t~. Vermiculitc. PlagJoclasc. ß1otite. RJtilc. /.~rcon, Magnetite. Dlck1tc, Nacritc, llalloysitc, Apatite. Titanite. Allanite. Chlonte. lllitc, Zoisitc. Clinozoisitc, Prehnitc. Scpiolitc, (ilauconitc, Kaolinite. Goethite. Calcite, Scricitc. Gibbsite. Nontronitc. Cordacritl!. SGM9C QuartL. K ldd,par. MuscO\ 11e. Hornblende. Epidote. Vermicuhte. Plag.Jocla:,c. Biotitc. Ruule. Sphene. brcon. D1ckue. Nacnte, llalloysite. Magnetite. Apatite. Titanite. Chlontc. lllnc. /.oi,ite, Allannc. CIJnotmsltc. Prchnitc, Sepiolite. Glauconitc. Kaolinite. Goethite. Sericitc. Gibb>itc. Calcite, Nontronitc, Montmorillon1tC, Pal ygors ~it c, Cordicritc. Sente DGMIOA Quart;, K feldspar, Biotitc. \1uscovite. Rutile. Ep1dotc. Vermieul ite. Plagioclasc. lliotitc. Mtbcovitc, Rutile. Dickite. aerite. Chlorite. Srhcne. Z1rcon, Magneutc. Glaucolllte. Zoisnc, Goethite. i\pautc. Tnanitc. Allanilc. Calcite. DOMlOB Quartz. K fcld>par. Biotuc. ~lusco\lte. Rutile. Ep1dotc. Verm1cuhtc. Plag10clase. Srhcnc. Zircon. Magnetite, Dicknc. acritc. Chlornc. Apatnc. Titanite. Allanite. Gh.nu.:onitc. 7oi::.itc. Goethite. K DGMIOC Quanz. K l~ld;par, Biotitc. Museovite. Rutile. Epidote, Venniculitc. Plagioclase. Zircon. Magnetite. Apatite. Dickitc. Naeritc, Chlorite. Titanite. Allanitc. Glauconitc. /.o"itc. Goethite. Kaolinite. Sep10litc, lllitc. Calcite. 1-- Seale DGMIIA Quartz. K feldspar. Biotitc. Musco•ne. Rutile. Epidotc. Vcrmieulitc, l'lag1oelase Sphene, Z~rcon , Magnetite. N~critc. C'hlorne, Zoi,ite. Aratitc. Tita111tc. Allanitc. Clino70isllc, Cioclhite, Calcne. DGMIIB Quartz. K feldspar. ßiotite. Musco\ ite, Rutile. Epidote. Vermiculite, Plagiocla>c. Sphene, Zircon, Magnetite. Nacrite. Chlorite. Zoisite. t\ratitc. Titanite. tdlanitc-. C lin oLOi~itc. Goethite, Calcite. DGMJIC Quartz, K feldspar. Biotite. Musco' ite. Rutile. Epidote. Vcnniculite. Plagioelasc. Zireon, Magnetite. Apatite. Naente. Chlorite. /.oisitc, T1~Ullte . Allanite. ClinoLoi,ne. Goethite. Calcnc 56 Table 8: Mincralogical characteristics of the smdied rccovcred artifac1s in relatio n 10 the pro filc depth. ~10RPIIO- SAMPLE ESSE TIAL MINERALS ACCESSORY MINERALS SECO DARY 1\II'JERALS LOGY OF DETERIO- RAT ION Sand di,. SGM I2A Quart«. K fcldspar, Muscovilc. llornblcndc. Fpidotc. Vcrmiculitc. aggregattoll Plagioclasc:. ßiotrtc. Rutile. Sphene. Zircon. Dickitc. acrite, llalloy;itc, Magnetite. Apatite. Titanite. Chlorite. Glauconote. Zoisitc. Allanitc. ClinoLoisite, Prchnite. Kaolinite. Scpiolitc, lllite. Calcite. SGM12\\' Quartz. K feld;par, ~lu scov ite. llornblendc. Eptdotc. Vcrmiculitc. l'lagiocla.sc. Biotitc. Rutile. Sphene, Z ircon. Dickitc. Nacritc. l-lalloysile. Magnetite. Ap~Hitc. Titanite. Chlonte. Glauconitc. Zoisitc. Allanitc. Clino/l..>bitc, Prchnitc..·. Kaolinite, Scpiolitc. lllitc. Calcite. Aheolilatio SGMIJA Quartz. K fcld;par. Mu Table 9: Chemical analyses of ASGQ corc sample in rclation to thc profile d cpth . StO AI,O Fe,O, K,O 'la,O CaO \igO P,O, so Cl ·r.o, \lnO Cr,O, L.O.I TOTAL '< \SGQI 60.58 16.93 h.S6 3.99 3,12 2.99 0.61 0.11 2.98 11.3~ 0.85 0,1 0 0.9X 100.4-1 \SGQl (~l.lX 17.96 654 lOS ~.XX 2.78 1!.59 O.IJ 3.01 0.31 11.85 0.1 0 1,07 100.48 ASGQJ 60.01 17.84 6.7X 3.89 3.1 2.83 0.55 0.1~ 3.12 11.)5 0.83 0.1 1 0 0.93 100.48 ASGQ4 60,79 17.3 4 6.23 4.29 2,98 2.97 (1,62 0.13 2.97 0.25 0.8 0.1 0 1.02 100,49 ASGQ5 60.52 16.95 6.X7 4.38 3,29 2.95 0.51 0.15 2.39 0,34 0,81 0.11 0 O.X9 100.16 ~SGQ6 61.11 16:8 6.1 4.49 2.93 1.S1 0.57 0,14 l.H7 0.32 0,86 0.11 () 0,95 IIXJ.05 ,\St.Q7 (<1:/~ 11.25 >.hl 4.71 3.11 ~.7~ 0.67 0.15 1.98 0.2~ 0.&7 11.11 II O.H7 100.23 ASGQ8 IH,I9 16,05 6,18 4.1H 3.2~ 1,21 0.72 0.1 ~ 1.87 0.26 0.79 0,13 0 0.97 100.39 ASGQ9 (>7, 16 15.68 5.113 4,81 3.34 1.08 0,69 0.16 0.11 0.31 0,82 0,12 0 0.89 100.2 ASGQ10 M.~ ~ 15.21 5.65 4.94 3,3Q 1.11 0.7 0. 16 0.11 0.25 0.79 0,11 0 0,99 100.35 ASGQII 67.02 14.87 5.55 ~.89 3.6~ 1.23 0.71 0.17 0.(19 0.25 0.'6 0,13 0 0,92 100.28 \SGQ12 67.08 14.25 6.11 4.83 J.IH 1.31 0.71 O.IS 0.08 0.27 0.72 0.12 0 0,9(> 100.26 ASGQ13 67.98 14,12 4.98 4.71 3.8~ 1.45 0.76 0.19 0,1 0.24 0.75 0.11 0 0.87 100,15 ASGQI4 67,83 14.54 4.67 4.81 3,86 1.49 0.75 0.19 0.09 0.2 1 0.67 0. 11 0 0,83 I(IIJ.05 ASGQ15 67.19 14.46 4.79 5.118 3.95 1,87 11,73 0.23 0.08 0.22 0.71 0.12 (I 0,69 100.12 ASGQI6 67.41 13.89 ~.99 4.9) 3.~1 1.92 0,72 0.2 0,09 0.23 0.72 0,13 0 0.91 100.05 ASGQI7 67.'9 14.1 4.78 5.09 3.S8 1,'19 0,73 0.19 0.07 0.21 0.74 0.13 0 0,78 100.48 ASGQIS 67.8 13.69 5.28 4.93 3,95 1.96 0.7S 0.23 0.02 0.25 O.IH 0,14 0 0,83 100.5 ASGQ19 67.8(> 14.04 4,88 4.96 3,87 2.1)1 0.74 0.21 0,04 0.2 0.71 tl.ll 0 0.77 100.42 ASGQ20 67.98 13,89 4.53 4,94 3.97 1.97 0.75 0,23 0.05 0.21 0.69 0,13 0 0.81 100.15 57 Tablc 10: Chemical analyscs ofADGQ core sample in relation to thc profile depth. SIO, Al10 1 Fc,O, K10 Na10 CaO MgO P,O, so, Cl Ti01 MnO Cr,O, L.O.I fOTt\L% ADGQI 66.22 16.91 3.2 1 4.07 2.98 2.23 0. 11 0.05 2,94 0. 14 0.24 Tr:-~rc 0.02 0.95 100,07 ADGQ2 66.13 16.44 3.33 4,31 3.11 2.6 1 0.12 0.04 2,99 0. 17 0.11 Trace 0.01 0,89 100.26 ADGQ3 66,99 16.75 2.99 4.67 2,91 2,19 0,1 0.05 2.56 0.1 6 0.21 0.01 0.02 0,87 100,48 ADGQ4 65 .88 17.21 3.11 4.91 3.15 1,99 0,2 1 0,03 lAS 0.12 0,18 Tracc 0.01 0.99 100.27 ADGQ5 65,91 16,94 3,25 5,12 2.94 2.07 0.2 0,04 2.65 0.17 0.2 0.01 0,02 0,79 100,31 ADGQ6 65,59 17,34 3. 17 4.97 3,32 1,97 0.09 0.04 2,59 0,14 0,1)9 0,02 0,02 0.92 100,27 ADGQ7 67,26 15,96 2,88 5,08 3,23 2, 11 0.28 0.03 2,47 0,12 0,1 0.01 0,03 0.93 100.49 ADGQ8 68, 16 15.89 ~ . q; 4.54 2,97 1,88 0.25 0,04 2.44 0.13 0.09 0,03 0.04 0,87 100,28 ADGQ9 71.32 15,44 2,98 l97 3.16 0,99 0.28 0.05 0 0,1 4 0,1 1 0.04 0,04 0.83 100.35 ADGQIO 71,54 14,98 2,65 5.21 3,33 0.79 0.31 0.04 0 0.13 0,1 0.04 0.05 0,91 100,08 ADGQ II 71,67 15,09 2.67 4,99 3,52 0,69 0 36 0.05 0 0.1 I 009 0,04 007 0 Q1 100,2 ~ ADGQ il 71.65 14,94 2,77 5.24 3.24 0,98 0.23 0.06 0 0.1 0,08 0.06 0,06 0.94 100.35 ADGQ13 71,71 14,45 2.28 5.)1 3,58 1.41 0.33 0.06 0 0.09 0.07 0.05 0.05 0,86 100.25 ADGQ 14 71.83 14,34 2,41 5.45 3.61 1.39 0.18 0.05 0 0,1 1 0,1 0,04 0.06 0.82 100,49 ADGQ15 71.74 13.% 2.34 5,65 3,72 1,56 0.26 0.05 0 0,09 0,08 0.04 0.07 0,87 100.43 ADGQ I6 72,11 13,66 2,21 5.47 3.63 1,52 0.37 0.06 0 0.08 0,09 0.05 0,07 0,97 100.29 ADGQI7 71,9 14,18 2JS 5..\ 1 3.59 1,42 0,35 0,06 0 0,09 0.06 0.05 0.08 0,88 IOOA5 ADGQ18 71.84 13,96 2.32 5.73 3.61 1,39 0,39 0,07 0 0.09 0.06 0.06 0.09 0.76 100.37 ADGQI9 72,2 1 13.78 2,27 5.61 3,56 1,54 0.34 0.07 0 0.1 0.06 0.04 0.08 0.74 100.4 ADGQ20 71,96 13,81 2.23 5,66 3.65 1,49 0.37 0,07 0 0.09 0.06 0.05 0.09 0.79 100,32 Tablc J J: Chcmical analyses of the samples from thc studied recovcred artifacts in rclation to the profi- Je dcpth. SiO, A120 1 Fc,O l K10 \a20 CaO MgO P20} so, Cl Ti01 MnO Crp3 L.O.I TOTAL ' o SGM IA 56.07 17,65 4.76 3.33 3,54 2.46 2.11 0.2 4,23 3.54 0,62 O.il'J 0 1,7 1 100.31 SGM IH 46,44 19,56 6,55 3.54 4,45 3.07 2,44 0.27 3,78 4,66 1.29 0,18 0.02 4.06 100.31 SGM IC 45,63 20.12 7.33 3,45 3.88 2,99 2.34 0.4 4,7X 4,07 1,02 0, 16 0.09 3,81 100.07 SGM2A 56.02 18.22 5.02 ).61 3.Jg 2.05 2.15 0.1 3.44 3,65 0,09 0.3 7 0 2.11 100.21 SGM21l 49.05 18,45 6,52 3.87 4.23 2,11 2,39 0.42 3. 12 4,22 2.94 0.24 0 2.88 100.44 SGM2C 45.98 19.54 8,11 3.96 3.41 2,16 3.13 0.38 4,65 3.89 1,3 0.05 0 3,85 100.41 SGM3A 55.4 3 18.03 5.06 3.13 3,11 2,33 2.54 0.13 3.88 4.03 0.34 0,1 0 2.07 100, 18 SGMJU 48.56 19.06 6,57 3.34 J.X7 2,87 2,75 0.]7 3.33 4.56 2,0'1 0,24 0.03 2.67 100,31 SGM3C 44.01 20.11 10,34 3,22 3.56 2,92 2.88 0,4 3,92 4.44 1,43 0.2 0.05 2.73 100.01 SGM4A 55,03 18.45 6,08 2.99 3,44 1,86 2.23 0.06 3,78 3.91 0.05 0.11 0 2.46 100.45 SGM4ß ~9 . 12 20,05 7,03 3,2 1 3,53 2,77 2,54 0,13 3,42 4,31 1,5) 0,06 0,09 2,66 100,45 SGM4C 45.23 20,45 11,1 .1.34 3,63 2,33 2,61 0,19 3.98 4.06 0,5 0,1 0,03 2.54 100.09 SGM5A 56,12 18.67 6.3 3 J,OX 2,88 1,87 2.09 0.04 3,98 3,22 11,05 0, 29 0,01 1.78 100.41 SGM5ß 48,44 22,14 7.2.l 3,22 2,98 2,18 2.18 0.05 3.31 3,87 0,38 0 0,09 4.2> 100.32 SG~I5C 46.6o 22,54 7.37 3,88 3,33 2,68 2.22 0,14 4.07 3.)6 0.15 0.04 0 3.78 100.42 SG~I6A 55.21 18,23 6.77 2,92 2.79 1,99 2.24 0,1 ~ . II 3.41 0,19 0.01 0.05 2.22 100.26 SGM6B ~3.24 22.3 7.36 4,58 3.66 3.55 2.37 0.43 3.43 3.98 1.45 0,18 0,09 3,45 100,07 SGM6C 44.3) 21.31 6.99 4,77 3.77 4.14 2.46 0.58 4.16 3.78 0.37 0.04 0.08 3.33 100.11 SGM7A 57.44 20.22 1,33 H9 2.89 2.79 2.02 0.1 1 3.99 3,34 0,3 4 0,12 0 2,67 100,15 SGWil 52.81 22.89 0.64 3,37 3,24 3,19 2,33 0.13 3.24 3,79 0,89 0.07 0 3.69 100.28 SGM7C 51.03 23.11 0.53 4.48 3,27 3.08 2.~ 7 0.17 4.15 3.88 0,66 0,14 0,06 3,42 100,45 SGMSA 54.11 18,45 6,33 2.87 3,0 7 3.11 1,89 0.116 3.96 3,18 0.09 0 0 2.94 100.06 SGMSß 47, 19 19,13 8.44 3,77 3.35 3,65 2,08 0,29 3.47 3.68 1.39 0.14 0 3.89 100.47 SGMSC 46.54 20.25 8.94 3. 18 3.21 3.22 2.12 0.12 4.08 3.54 O,Sii 0.06 0,04 4,51 100.37 SGM9A 53.12 18,05 5.55 3.27 l\3 3.22 1.99 0.1 4.21 1.21 0,4 0,03 0 3.8~ 100,12 SGM9B 46.1 20,13 7.11 5.45 3.46 3,44 2,25 0,13 3.89 3.73 0.5 7 0,05 0 4,12 100.43 SGM9C 42 ,13 20,14 9.75 5,89 3.32 3.54 2.21 0.14 4,13 3.66 0.49 0.05 0 u 100.25 DGMIOA 56, 14 19.34 3.1 3.08 2.89 2.89 2,15 0, 1 4.26 3,11 0.28 0,34 0 2,34 100,02 DGMIOß 49,04 20,1 4 4,34 4.48 3,54 3,98 2,26 0,15 3.48 3.78 1,18 0,1 0.08 3.87 100.42 DGMIOC 46.08 23.54 4.99 3.5i 3.39 2,95 2.23 0,34 4.2 3,56 0.72 0,47 0.08 4,05 100, 17 DGMIIA 56.29 19,32 ~.25 3. 12 3,22 3.32 1,95 O,o> 4.14 3.07 0.16 0,02 0.08 3.11 100,08 DGMIIB 48,36 20,31 3,67 4.88 3.61 4.9 2,11 0.06 3.69 3.86 0,2 3 0,03 0,09 4.56 100.36 DGMIIC 48.07 21,33 4,56 3.98 3,52 3,16 2.08 0.04 4,23 3,67 0,14 0.02 0,09 5,11 100 SGM il A 50,89 20,27 5.66 3.54 3.75 3,14 2.23 0.24 3,97 3.4) 0,6 0,09 0.08 2.23 100.06 SGM I2\V 46.44 21.11 6.61 4.61 3.92 3,6 1 2.67 0.27 3.76 3,99 0. 8 0.12 0.06 2.4 5 100.42 SGM 13A 49.88 19,44 5,33 3.98 4,12 3,23 2.28 0,2 4,23 3,55 0,69 0, 1~ 0,1 3,1 100.21 58 Table II: Chcmical analyscs of lhc samplcs from thc studied recovcrcd anifacts in relation to the profi- lc dcpth. \1 0, t'3;0 (I ~lnO I s.o, 1 Fe,O, K,O CaO \lgO P,O I so, TIO, Cr,O, L.OI TOTAL '• SG\1131\'I ~~.1 1 21Ah 7.08 ~.-s ~.(>5 3.i6 1..1~ I o2 I 3,89 3.89 0.~8 0.17 0.1 3,3 100.~ SG\1 I~A I 50.13 10.110 ~.I ~ 3.~1 3.13 1W ~A' I 0.51 I -451 3.46 o: 0.09 0.11 2.76 1110.33 ~G\JI~W I ~5.31 12,01 6.88 3.77 3.55 3.58 1.65 I 0.49 I ~.05 ~ .os 0.9 0.1 IJ.I} 2.X9 1110.5 Legl'nd: ASGQ: Aswan ro'c granirr quarnc ~ AllGQ: Aswan red g,ranite qua rrics SG\1: Ro)C grumte monument DG\1: K~d gramtl" monum~nt A: ~tonun'k!nt :.ubslr:nc B: uperfi~tJI de'tachcxlla}'-'f (: IXpo'IIIS \\ere IOund at tth! monumcnt detachetlla)~r lrl!!rfacc W: \\('tlth~rcd 'urface Oiscussion: - The petrophysical characteristics: The petrophysical properlies of the weathcred samples show on one hand that the open porosity, Saturation cocfficient and watcr sorption are quite high as a compari son with thc same properlies of thc frcsh samples, and this indicates to that physical alteration is considerable, and on the other hand the density is relativcly low, and this indicates to that chemical alteration is also considerablc. Also according to these results wc think that the artifacts (group II ) suffered from physical alteration more than the othcr of (group I) where we can easily obscrvc th at the opcn porosity, satu ration coeflicient and water sorption of SGM 12, SGM 13 and SGM 14 arc quite high as a comparison with thc othcr samples. - The mineralogical analyses: From the rcsults of the mincralogical study with XR.D we can affirm that the chcmi cal alteration of the granite in its quarries in Aswan is much slower than that of the same stone of the rccovered artifacts, whcrc the numbcr of the weathering prod ucts and their quantities are vcry little in the fresh quanies samplcs as a comparison with thc weathered samples from artifacts although the alteration process began in the quarries somc million years ago and the evolution process of altcration began under seawater on ly ahout 1500 yea r ~ ago. This reOects the vcry big di fference between the two kinds of environments, the quarries and the marine and also emphasizcs the role of the environment in the dccay processes. We can say that in both of them thc rate of alteration decreases in ward, where ASGQ core sample contained 4 clay minerals up to 7 cm depth , 3 minerals up to 16 cm and only two up to 20 cm, and also ADGQ corc sampl e containcd 4 clay mincrals up to 13 cm depth, and 3 mincrals up to 20 cm as shown in figs. 19 and 20 respcctivcly. But in the casc ofartifacts we observed that most ofstudied artifacts (group I)) have weat hering products at the monumcnts dctached layers intcrfaces more than in the wea thered detached layers. 59 And we suggest that the rate of alteration also decreases in ward, and this phenome non is due to the action of sea waves where intensive drainage may be take place at the artifacts surfaces. Stati stical study were perfonned to calculate the occurrence times and the numbers of weathering products which were found in the all studied fresh and weathered samples and the first observation whi ch was obtained may be support o ur suggestion where the weathering products in the detached layers of artifacts numbers SGM3, SGM 4 and SGM7 are more than at their monuments detached Jayers interfaces, and equal in artifacts numbers SDM II , SGM 12, SGM 13 and SGM 14. The second observation is that the most little total number of weathering products were found in artifact number DGMll and this artifact is one from the only two stu dicd artifacts which belong to Aswan red granite varicty and thc other one number DGM I 0 has also relatively little number ofweathering products as a comparison with the other atrifacts, and as a result of this observation we suggest that the red variety of Aswan granite is more resistibility and durability than the rose variety, and the good preserved state ofthese two artifacts (personal observation) may be support our deduction, and this may be due tothat the biotite content in Aswan red granite is more little than in the rose granite where the results of XRD proved that the Biotite is con sidered an accessory mineral in the red variety and essential in the rose and also the results of XRF Support that as will be explained in the discussion of XRF results. The third observation from this statistical study concerns with the occurrence times of weathering products where it was found that thc vermiculite has the most occur rence times (102 times) in 79 studied samples from artifacts and quan·ies either as a separate mineral or as a mixture with chlorite and montmorillonite and fig. 22 shows a comparison between the weathering products in their occurrence times in the stu died samples. We can explai n that according to what was mentioned by (R. Pellizzer and G. Sabati ni, 1976) where the rate at which minerals are attacked varies especial ly because of differences in their structures, and it is not by chance that the order of increasing stabili ty with regard to supervene alteration corresponds to the order of crystalli zati on of the minerals from a silicate melt, as established by (N. L. Bowen, 1956) see fig. 23. Another reason may be explain the very high occurrence timcs of vermiculite that the structure and properties ofthe vermiculite minerals appear inter mediate between those of the chlorites and montmorillonites (F. C. Loug hnan, 1969) anrl this means that the possihility of its occurrence may he hig h either separately or as a mixture with them. Also we suggest that when the stone has a Iot of minerals which can alter to the same weathering product, the possibility of the increase of occurrence times of this weat hering product will be high, for example in thc case of the vermiculite the granite minerals whi ch can alter to it are feldspar, biotite, muscovite and bornblende as shown in table 12. And there is no doubt, that the circumstances which prevailed around the artifacts control the kind of weathering product and also the times of its occurrence namely the 60 pH and Eh values specially and the influence of Fixation and Chclation on the mobi lity of cations to some extent. Another very important result was obtaincd from XRD analyses concerns with the cordieritc which we have qualificd as a weathering product and not as accessory mineral as it is known in some granites (see Table 8). and we can explain that accor ding to the XRD patterns of ASGQ, ADGQ core fresh samples and SGM9. Which can be scen in figs. 19,20 and 21 respectively and after a compari son between them we can observc that thc main peak of cordierite uppears only in the last pattern in fig. 21 whi ch represents the weathered artifact samples, and also wc can observc in thi s figure separately that its intensity is very high in the weathered dctached layer and under it as a comparison with the artifact substrate, and this supports our qualifica tion of cordierite as a weathering product and not as an accessory mineral and we sug gest that the principal mineral from which was altered is biotite as shown in table 12 which contains the most probably alteration of the essential and accessory minerals of thc weathered granite under seawater. - The chemical analyses: The chcmical study with XRF has shown that the content of Si4 in A DGQ corc sam ple is morc than in ASGQ core sample, and on the contrary the content of Fe3 in the first is lesser than in the second (see figs. 24 and 26). The variations in Si 4 and Fe' contents may bc due to the variation in the quartz and the biotitc contents respcctively, and this support our last mentioned suggestion ofthe good re istibility and durability of Aswan red granite variety as a comparison with its rose variety. XRF analyscs also have shown a slight decrease in Si• , K ', Na ' and Mg' conccntra tions in the outermost zone in both ofthe two studied core samples as shown in figs. 24, 27, 28 and 30 respectively. and on the contrary somc increasc in AP and Fe' con- Table 12: The most probably alteration of rose and red granite under seawatcr. The principal minerat Thc "cathering products I K fc ldspar ~crit:i t t=. \t.:l miculitc. nlo:l tmorillonite. chloritc- 'crmiculite-montmorillo- nitc. illite. kaolinite, dickite. nacritc. gibbsitc. prehnitc. halloysite. 2 Plagioclase zoisitc. c linozoisitc. scricitc. prehnitc. cpidote. halloysite, calcite. 3 Biotite Vermiculitc, chlorite, prchnite. sericite. epidote. glauconite. gibbsite. goethitc. mon tmo ri llo n it~. cordierite. 4 Museovite vermic ulit~ . montmorillonitc. (kaolinite. dickite, nacritc (?)). 5 Hornblende (chlorite and epidotc) or (chlorite and calcitc), bcide llite. gibbsite. 6 Magnetite goethite. 7 faya lite (Olivine) palygor,kitc. sepiolite. nontronite. saponite. hectoritc. (which cxists in a fcw cascs with amphibolc) 61 centrations in the outermost zone also in both of them as shown in figs. 25 and 26 respectively. The behaviour of the Ca2 ion in both of the two varieties has shown very clear vari ation from the outermost zone to the inner and between them, where its concentration was quite high at the surfaces and up to depths of 7 cm and 8 cm in thc rose and the red varieties respectively but after these depths it suffered from very clear decrease may be up to 14 cm and 12 cm depths respectively and then its concentration revea led some increase again up to 20 cm deptb as shown in Fig. 29. The L.O.I. (loss on ignition) has shown that there is some increase outward in both of the two core samples as shown in Fig. 31. We can explain that as follows: the slight decrcase of Si•• may be due to some granu lar disintegration which due to di tferent physical factors attacked the outermost zone and hencc loss of some quartz, but the decrease of K , Na' and Mg2 is due to some chem i c~tl leaching. 2 We attribute the increase of Ca ' in the outermost zone of thc two core samples to the formation of gypsum and the dccrcase of it in the middle zone to the leaching process. 3 The some increase in Al'' and Fe · concentrations in the outermost zone is due to the sta bility and immobility of the first in the circumstances of pl-1 values between 4,5-9,5 and of the sccond in the oxidizing circumstances. The increase of L.O.J. in the outermost zone may be due to some increase of clay minerals and salts and this also corroborates with the last mentioncd XRD results of the increase of the clay minerals in the same zone. In the case of the studied artifacts we found that Si 4 concentration decreased dramati cally specially o utward in both ofartifacts (group I) and (group II) as shown in figs. 32 1 2 and 40 respectively, but the concentrations ofK, Na-, Ca • and Mg " have shown some increase at the weathered surfaces and under thcm more than in the monuments sub strates as shown in figs. 35, 36, 37 and 38 for artifacts (group I) and figs. 43, 44, 45 and 46 for artifacts (group 11) respectively. On the contrary the concentrations of Al'' and Fe' ions were very high specially in the superficial detached layers samples, in the deposits under them in the case of arti facts (group 1) and at the weathered surfaces in the case of artifacts (group II) except in the samples of artifact 11L1111ber SGM7 which have recorded a vcry clear depletion 3 in the Fe ' ion concentrations specially in the detached layer andin the deposits under it as shown in figs. 33 and 34 for artifacts (group I) and figs. 41 and 42 for artifacts (group II) respectively. The loss 011 ignitio11 results of artifacts (group I) samples also in dicate tothat the loss 011 ig11ition in the weathered detached layers and the deposits which were found under them is more than in their artifacts Substrates as shown in Fig. 39 and in the case of 62 artifacts (group II) samples thcre is al so some increase at the weathered surfaees more than in their artifacts substrates as shown in Fig. 47. From the above mentioned we can say that the behaviour of alt elements indi cates to that the rate of leaching is progressive inward moving mechanism o f decay and we can attribute the high concentrations of alkalis at the surfaces and under them to the formation of vario us salts in a later stage of deterioration namely after the artifacts recovering. We dcpended also in our attribution ofthc inercase ofalkalis to the salt fom1ation on our determination of the minerat salts in the aqueous extracti on from the studied samples with atomic absorption and ionic chromatography and also on the mineralogical study of samples with X-Ray Diffraction and with the electron microscope but the results which were obtained will be published in aseparate paper for the second stagc of decay. 4 Although the Si ' ion is lost slower than the alkalis ions under leaehing conditions, it suffcred from a very distinct decrease specially in the parts ofthe alkalis increasc, and this is considered also a sure proofthat the alkalis also were leached and their high concentrations at these parts from artifacts are attributed to satt formations as last mcntioned. We can not attributc the decreasc of Si4 ion to the physical alteration as we attributed it in the case ofthe quarries as last mentioncd becausc in the casc of artifacts the high decreasc o fthis ion extencled to the artifacts Substratesand did not restriet at thcir sur fa ces. As regard to the behaviour of Al' ion the authors think that the pH values ofthe mari ne environment where thc studied arti facts were di scovered did not lie outside the range of about 4 to 9 because the Joss of this ion out this range are possible and the concentration of it in the studicd artifacts were found very high specially at thc sur faces and under them where the rate of chemical leaching is vcry intensive. The concentrations of Fe1 ion were very high in the alt studied artifacts except in one artifaet (SGM7) which contained a very low Fe' concentrations specially in the dcta ehed laycr and under it and we can explain that accorcling to thc classification of the sites ofthe studied artifacts wirhin the marine environmcnt associatcd with thc reactions interfaces which was graphical represented in fig.lO and also to the position ofzcro Eh in respect to the seawater I sea bed sediments as shown in (fig.l2) where we suggcst that the artifact (SGM7) was one from the few artifacts which werc buried under the seab ed sediments at depths between 50 to I 00 cm where a reducing circumstances prevails specia lly when the rote ofthe sulphate reducing baeteria was taken into account, in this case the reduction ofFe 3 to Fe 2 greatly inereases their solubility. On the contrary in the case of the other artifacts which were diseovered on the seab ed where oxidizing conditions prevails the Fe+ 3 ion is immobile and also the oxida tion of Fe z to Fe'' is the expected reaction specially in the case o f pH increasing and Eh decreasing and hence the concentration of Fe·3 will be very high. 63 The results of L.O.l. corroborated with the others of XRD and XRF where the incre ase of it in the last above mentioned parts of artifacts can be attributed to either the high quantity of clays or salts or both of them where the lost crystallization water of these products indicates to their quantities to some extent. - The petrographic study: As a result of this study we can divide the studied samples to 3 Ievels according to their degree of alteration. These Ievels are from I (the most persevered) to 3 (the most al tered) as shown in tablc 13 . The characterisation ofthe alterati on Ievels were made from the comparison between th e all studied samples thin sections under the polari zing microscope and from the precise observation ofboth physical and chemical alte ration features which affected them. From aforementioned in table 13 we can say that the severe alteration which affected the studi ed monuments (Ievels 2and 3) is considered the most advanced degrcc of alteration which was inherited fro m the quarries (Ievel I). Tablc 13: Petrographical Index ofthc alteration Ievels ofthe studied samples associatcd with thc granite decay morphologies which arise in every Ievei. ldentification Level of Oetected Oescription of alteration state of samples alteration moq1hology Fresh from I No morphologies Short isolated micro cracks in both of quartz and quarries arise in this Ievei. microclinc. Somc of these micro cracks are open and thc othcrs are tight. Somc of thcm may bc filled with some new Formation minerals. (See Figs. 48 and 49). Weathered 2 Superficial Micro fi ssures Of different lengths isolated and from artifacts detachmcnts conncctcd affecting mainly quartz and microcline. (group I) (plaques. Most of these micro fissurcs may be filled with plaquettes and weathering products and other minerals. Microcline scales). has slighr grittiness and dusty appearance from tiny alteration. Bleached. Clear chemical alteration in thc ouler weathered layers especially in mica and amphi- bole and decrcases in ward, (See figs. from 50 to 53). Weathercd 3 Sand disaggre- Extremcly micro and macro fissures of different from arti facts gation, lcngths and widths affecting mainly quartz, microelinc, (group II) Etch-pitting plagioclase and to a lesser extent biotite. A ll of them (alveolization) are conncctcd to form an appreciable network of and Fissuring. inter-, intra- and transgranular micro and macro fissures. More abundant in quarlz and miaocline. The fi ssures are propagatcd dimensionally along two or three weil dcfincd preferred orientations. Plagiodase and microcline have grittiness and dusty appcarance from alteration. The microcline has a bleached colour. Grain boundaries arc opcn. Clcar chemical alteration in both of the outer and the inner parts of samples. Thc chemical alteration products did not only restriet in the inner parts in the micro and macro fissures but also occupied somc grains pans. (See figs. 54 and 55). 64 We can also deduce that there is a directly proportional relation between the physical and the chemical alteration. Therefore we think that the physical alteration Ieads to the chemical alterati on and in this case thc fissures play very important role in the chemical alteration process. We can summarise this role of fissures considering them (tubes of the chemical lea ching) wherc they on one hand a ll ow the sea water and the other decay agents to acccss insidc the granitc and on the other hand facilitate thc removing ofthe different cations and sil ica which release as a result o f the granite parent minerals bre::~k in g down. Conclusions: The deterioration of thc recovered granitc artifacts has already begun in a very slight degree before thc extracting of their stone from Aswan quarries and ccrtainly before the birth of arti facts and the date of thcir sinking under scawater. We can affirm that the alteration of the granite stonc of a monument is much faster than that ofthe same stone in its natural environment and thi s contrasts wilh what was mentioned in (R. Pellizzer and G. sabatini, 1976) where we recorded 24 weathering products in the studicd samples from artifacts versus on ly 5 in the studied samples from thc quarries. Wc can affirm that thc most serious alteration which affects the granite is the physi cal and not thc chemical. Also we can consider that the physical alteration is the main Ieader to the chemical alteration. The different granite decay morphologies can be main1y attributed to the different degrecs of physical alteration. The most likely arrangement for the granite decay morphologies according to their degree of decay from the lower to the higher is: Scales ..._ Plaquettes _,... Plaques _,... Sand disaggregati on ..._ Alveolization _"_ Fissuring Wc suggest that the three clay minerals (halloysite, palygorskite, and sepiolite) as weathering products are considercd an indicator tothat the cnvironment where grani te artifacts were found is a marine or Iake or at least an environment of very high humidity especia lly in the case of hall oysite occurrence. Although the two minerals nacrite and dickite have not bcen recorded as a products of wcathering as Loughnan, 1969 mentioned, both of them occurrcd in the studied artifacts 36 timcs. 65 Also in the quarries core samples nacrite and di ckite were recorded 7 and 16 times up to 7 and 16 cm depth respectively in ASGQ core sample and only nacrite has recor ded 13 tim es up to 13 cm depth in ADGQ core sample. We can record that cerdierite occurs in so me granites not only as an essential or accessory mineral but also as a weathering product. Although the presence of calcitealso as a wcathering product in granite is not famous, we can consider it in thc case of its occurrence in the granite an indicator to that the alteration process to which the granite subjected was very severe. There is no doubt that the sa lts play an important rote in the evolution of the superfi cial detachment morphology and thi s point was also researched but has been publis hcd yet. References: ACASO, C. 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